1. Field of the Invention
This invention relates to a method of producing composites capable of being used as superconductors. More specifically, it deals with wires composed of extremely fine filaments of niobium and niobium alloys and a process for producing the same.
2. Description of the Prior Art
In the past, composites for the production of rods, cables, or wires were produced by laminating the metals or combining them in some way and subsequently fabricating them to final dimensions. Superconductors of niobium alloys have been produced in this way with various drawbacks.
As an example, methods of producing niobium tin wire having fine continuous filaments have been costly and unreliable because niobium rods are used for forming the conductor filaments. The components for construction have dimensions of 1/8" diameter or larger, thus requiring a great reduction to produce a wire with one micron diameter filaments. The wires are usually produced by placing the niobium rods in a bronze billet and extruding the billet several times to reach a certain size filament of the niobium rod. This wire produced is rebundled with other wires and again extruded. In the diffusion process whereby the tin in the bronze is diffused into the niobium, large Kirkendall voids are produced in the bronze when the niobium filaments are of large dimensions, over 10 microns. Large Kirkendall voids are detrimental to the wire.
Further, because these wires produced by the prior art processes are composed of individual and separate filaments, these filaments tend to break during the fabrication process because of being extruded from such a large diameter to such a small diameter. When individual filaments break, they cause a weakening of the bulk wire and eventually can cause the wire to break, thus decreasing the yield of usable product.
In normal present day processes, it is necessary to fabricate the wire billets through extrusion processes and to re-extrude several times to reach final dimensions where the wire is drawn through dies. Each of these extrusions is very hard on the filaments and is also very expensive to perform. It is, therefore, desirable that there be found another method of producing composites capable of being fabricated to form wires having fine niobium alloy filaments which are free of the detriments of past processes, i.e., expense and filament breakage.